Introduction to C

Introduction to C

Introduction

C is general-purpose, structured programming language, developed by Denis Ritchie in1972 at Bell lab USA.

Its instructions consist of terms that resemble algebraic expressions, augmented by certain English keywords such as if, else, for, do and while.

In this respect C resembles other high-level structured programming languages such asPascal and FORTRAN.

C also contains certain additional features, however, that allow it to be used at a lower level, thus bridging the gap between machine language and the more conventional high-level languages.

This flexibility allows C to be used for system programming as well as for applications programming.

C is characterized by the ability to write very concise source programs, due in part to the large number of operators included within the language.

It has a relatively small instruction set, though actual implementations include extensive library functions which enhance the basic instructions.

C compilers are easily available for computers of all sizes, and C interpreters are becoming increasingly common.

The compilers are usually compact, and they generate object programs that are small and highly efficient when compared with programs compiled from other high-level languages.

The interpreters are less efficient, though they are easier to use when developing a new program.

Many programmers begin with an interpreter, and then switch to a compiler once the program has been debugged (i.e., once all of the programming errors have been removed).

Introduction to C   How to open C program code window   Before opening C on your computer. Please ensure that C compiler has been loaded or not. If not then please load it first and then try any of the following ways to open C which suit your computer setting.   1.Start>>Program >> Turbo c.   2. If turbo C icon is present on your computer desktop then simply click on it.   3. My computer >>c:\>> tc (folder)>> bin (folder) >> tc.exe (icon).   4. Or make sure the path where you have loaded the C on your computer and try to run it from there.   After following the above instructions the screen which is given below will appear on your desktop:           Introduction to C   Description of C code window     1. =: Interface to external programs.   2. File: File related option such as opening and saving file.   3. Edit: Cut,Copy,Paste operation.   4. Search: Find,Find & Replace operation.   5. Run: Compile and run the file currently loaded in the text editor. And debugging such as setting/clearing trace points can be performed from this menu.   6. Compile: The menu item compiles a source file to an object file or an .exe file.   7. Debug: Provides interactive debugging. Variables can be examined/set/cleared, and we can watch variables change during execution.   8. Project: This menu item controls Borland C++'s handling of large programs that are in multiple source file.   9. Option: Default option are set during installation . The user can change any option at any time through this menu.   10. Windows: Windows operation include zoom, arranging windows on the screen , and closing windows.   11. Help: Borland C++ includes a context sensitive help capability. Select Help or press f1for general Help, Shift f1 for indexed help or Ctrl f1 for context sensitive help.         Introduction to C   Editing File     To open a new file, first press Alt F then Enter key, File pull down will activated, select newand then press Enter key, the display will be change into a blank screen of text editorhaving file name NONAME00.C, on which you can start entering your code through keyboard.   To open existing file press Alt F and then Enter, from the activated file pull down menu select Open, A Open Dialoge Box will appear, select desired file name path and pressEnter.         Introduction to C   Saving and Running a program   Press Alt F, move the cursor to save , press Enter and then type file name with extension.C in given Text Box and press Enter to save the program.   Running a program   Press Alt R to pull down the Run menu and Enter to begin compilation, A compile window opens and shows progress and output can be viewed in output window and press Alt W to pull down window menu, move the cursor down to output and press Enter. Press Alt W and move the cursor to close to close output window immediately.   Exiting Borland C   Press Alt X to Exit Borland C and return to Dos Prompt.       Introduction to C   The components of C language   There are five main component of C language are:   1. The character set: Any alphabet ,digit or special symbol ,used to represent information is denoted by character. The character in C are grouped into four categories.   1 Letters A...Z and a...z 2 Digits 0,1,2,.....9 3 Special Symbol ~,`,!,@,#,$,%,^,&,*,(),.,<,>,?,/,",:,;,{},[] 4 White Space blank space, Carriage return, form feed, newline, horizontal tab   2. The data types: The power of the programming language depends, among other thing, on the range of different types of data it can handle.   3. Constants: A constant is a fix value that doesn't change while program execution.   4. Variable: A variable is an entity whose value can change during program execution.   5. Keywords: Keywords are those word which have been assigned specific meaning in C language. Keywords should not be used as variable names to avoid problem.   Note: Above given all the term has been discussed in details in next section.         Introduction to C   Structure of C Program   Every C program is made of function and every function consist of instructions called statement.   Structure of C Program.   #include //stdio.h is the header file main() // main function is the first function which is executed by a C program.   All C statements are written within main function. {   // All C statements.   }   Functions   Every C program consists of one or more modules called functions. One of the functions must be called main( ). The program will always begin by executing the main function, which may access other functions.   Any other function definitions must be defined separately, either ahead of or after main.   A function name is always followed by a pair of parenthesis, namely, ( ). And all function statements are enclosed within a pair of braces { }.   The program execution always starts with main function. When the closing brace of the main function is reached, program execution stops, and the control is handed back to the OS (Operating System).   Statements   Single C language instruction is called a statement. Statements are written according to the grammar of C language. Every C language statement must ends with semicolon(;).   In order to write a C program we should follow some basic rules which are described below:   a) Usually all statements in C are entered in small alphabets.   b) Blank spaces may be inserted between two words to improve the program readability. However no blank spaces are allowed within a variables, constants or key words.   c) It has no specific rules for the position at which statements is to be retained that's why it’s often called a free form language.   d) All C statements must end with a semicolon (; )   Till now, We have very little knowledge about the type of variables, constants and keywords. Now we would try to understand the simple C program.         Introduction to C   A sample of C language program   Example of C program to calculate area of circle:     Explanation of above program :   # is the preprocessor directive which commands that the content of file should be included at the time of compilation.   < stdio.h> is the header file which contains all input and output functions like scanf(), printf() which are frequently used in c programs.   main() is the first function which is executed by a C program.   1. int a,r=5; -> This statement declares 2 variables a and r of type integer and r has been assigned a value of 5.   2. const pi=3.14; -> This statement declares pi as constant and value 3.14 has been assigned to it.   3. a = pi * r *r; -> This statement computes the area of circle and assign it to variable a   4. printf("%f",a); -> This statement prints the area of circle using printf function.   5. getch(); -> It is used to get character from user.   Note: /* Any thing written within it is consider as comment statements. */   For Animated Presentation(With Voice) Click here